The present invention relates to a zirconium dioxide powder, the method of its production and its use.
Zirconium dioxide powder can be used in very different areas such as e.g. electronics, ceramic components, fireproof materials and catalysis.
It is known that zirconium dioxide powder can be produced by flame hydrolysis (DE 36 11 449). The known zirconium dioxide powder has a surface area of 104 m2/g and a chloride content of 2.66% by weight.
The known zirconium dioxide powder has the disadvantage that it tends to cake in the flame reaction tube during production and therefore causes undesired interruptions of the operation.
An object of the present invention is to produce a zirconium dioxide powder not having these disadvantages.
In achieving the above and other objects, one feature of the present invention is a pyrogenically, especially flame-hydrolytically produced zirconium dioxide powder which is characterized in that the specific surface area of the zirconium dioxide range from 20 to 200 m2/g, the primary particles, which may be coalesced to each other, range from 7 to 100 nm in size, the tamped density of the deacidified and non-deacidified zirconium dioxides range from 40 to 150 g/l, the Sears numbers of the deacidified and non-deacidified zirconium dioxides range from 1 to 20 ml/2 g and the chlorine content of the deacidified zirconium dioxides is less than 0.6% by weight. The Sears number of the zirconium dioxide is the same as the range discussed above regardless of whether the zirconium dioxide is in the deacidified or the non-deacidified state.
In particular, the zirconium dioxide powder of the present invention can have the following physico-chemical characteristic data:
In accordance with another feature of the invention, the method of producing the pyrogenically, especially flame-hydrolytically produced zirconium dioxide powder is carried out starting with zirconium halides, preferably the chloride, which is evaporated, the resulting vapor is mixed alone or together with a carrier gas, e.g. nitrogen, in a mixing unit in a burner with other gases; i.e. air, oxygen, nitrogen and hydrogen. The gases are caused to react with each other in a flame in a closed combustion chamber to produce the zirconium dioxide and waste gases. Then the hot waste gases and the zirconium dioxide are cooled off in a heat-exchanger unit, the waste gases are separated from the zirconium dioxide and any halide remnants adhering to the zirconium dioxide obtained are removed by a heat treatment with moistened air.